This invention is concerned with apparatus for use in manufacturing containers out of glass, the apparatus comprising parison forming means operable to form a parison from a gob of molten glass, and transferring means operable to transfer a parison from the parison forming means to a mould cavity in the shape of the required container, the transferring means being arranged to position the parison so that it is suspended across an opening of the cavity. The invention is also concerned with a method of manufacturing containers out of glass comprising forming a parison from a gob of molten glass, and transferring the parison to a mould cavity in the shape of the required container so that the parison is suspended across an opening of the cavity.
In conventional apparatuses and methods for manufacturing containers out of glass, a gob of molten glass is formed by either a blowing or a pressing operation into a parison. When the parison has been formed, it is transferred, while supported by a divided ring (called a neckring) which grips a neck portion of the parison, to a mould in which the parison is blown to the required shape by the introduction of air under pressure into the parison. When the parison is formed, portions thereof which contact the forming elements become colder and therefore less viscous than the reminder of the parison and serve to retain the parison in shape as it is transferred. However, it is necessary for the parison to be of substantially uniform temperature for the final blowing to take place and, to achieve this, the colder portions of the parison are allowed to re-heat. This re-heating is achieved by allowing a period during which the remainder of the parison re-heats the colder portion thereof by a combination of conduction and radiation.
The above-described conventional apparatuses and methods for manufacturing containers are generally satisfactory where the container is to have a sufficiently thick wall that there is sufficient glass in the parison to allow self-re-heat as before described to take place. However, in the case of thin-walled containers, there may be insufficient glass present to allow such self-re-heating. It is possible to provide external heating for the parison as it is transferred to the mould but, if this is done, there is a risk of deformation of the parison before it reaches the mould and, since the parison's movement has to be stopped to enable it to be heated, the speed of manufacture is reduced. With conventional apparatuses and methods, it is not possible to produce thin-walled containers whose walls have a uniform thickness around the container. Accordingly, in order to provide sufficient strength for the containers more glass has to be included than would otherwise be the case.
It is an object of the present invention to provide an improved apparatus with which containers having thin walls can be efficiently manufactured.
It is a further object of the present invention to provide an improved method by which containers having thin walls can be manufactured.